1. Field of Invention
This invention relates to lightweight, collapsible stools and chairs used in camping, and other outdoor activities where easy portability is desired.
2. Description of Prior Art
Lightweight, collapsible stools and chairs are used in camping and other outdoor activities because they carry easily, stow compactly, and offer comfortable off-ground seating.
Some of the simplest devices for portable seating convenience have been three and four-legged stools with triangular or square seats. These simple designs offer low weight and good compactablity (i.e. maximum collapsibility) but lack long term comfort because they do not have any back support.
Four-legged chairs, which are more numerous in variety in prior art, show a constant trend to improve upon weight, compact-collapsibility, portability and comfort.
U.S. Pat. No. 2,353,090 to Faller (1944) is for a four-legged chair with an external center hinge with two front-to-back horizontal seat supports, and a back support shaped like an A-frame. Faller's design offers improved compactness and strength over prior art but the hard-surface A-frame is uncomfortable on the user's back.
U.S. Pat. No. 4,184,711 to Wakimoto (1980) is for another four-legged chair with the legs pivotally-coupled by an external center hinge and two back support uprights each hinged separately to a leg. Wakimoto's patent offers improved compactness over Faller's art by eliminating the horizontal seat supports. However, the external center hinge and the rigid back support tubes either interfere with free arm movement when angled out or cause discomfort as pressure on the fabric flexes the support tubes into the user's back. To minimize the before mentioned shortcomings the back support tubes and fabric are necessarily kept to a shortened size, thus describing and lessening the amount of support to the upper back.
U.S. Pat. No. 4,290,643 to Logan (1981) is a folding chair comprising a complicated network of eight rigid members, six tension cables, and a complex fabric cover. Although the closed bundle folds in a substantially parallel arrangement for collapsibility, the increased number of rigid members is not an improvement over prior art in terms of compact collapsibility. It also is not an improvement over prior art as to weight and ease of assembly.
U.S. Pat. No. 4,595,232 to Glenn et al. (1986) shows a four-legged chair with legs put together as two front-to-back X-shaped frames, two side-to-side horizontal seat supports connecting the X-frames, and two posts extending upright from leg sockets to hold a fabric backrest. A "spacer bar" reinforces the posts above the backrest to eliminate the flex of Wakimoto's art but adds a hard surface causing user discomfort. However, this design does not improve the collapsibility or lightweight features of existing art. Also, the rigid seat-front frame-member lies directly and uncomfortably under the user's legs.
There is another group of both three and four-legged chairs which are used in camping, and other outdoor activities. This group is sometimes referred to as "hammock style". (e.g., U.S. Pat. No. 2,712,349 to A. LeVoir (1951); U.S. Pat. No. 4,671,566 to Knapp (1987); and U.S. Pat. No. 5,362,130 to Hoffman (1994).)
These "hammock style" chairs suspend a full body-support sheet from lower legs in front to a higher leg or legs in the rear. Although comfortable once the user has reached the fully reclined position, a major shortcoming is their proximity to the ground making them difficult to get into and out of; and there is no direct support to specific parts of the user's anatomy. The hammock style chair frames are often heavy or cumbersome and not compactly collapsible.
Lightweight, collapsible chairs are characterized by small seats and short legs, which make a correspondingly small footprint, and with back supports positioned directly off rear legs. Therefore, stability becomes a factor when sitting on uneven ground or when tilting backward. With exception to the hammock style chair, including the Logan chair, the examples cited above are subject to reduced backward stability.